Method for producing components from mmcs (metal matrix composites) using a powder that has been melt-atomised in an inert gas atmosphere

ABSTRACT

The invention relates to a method for producing components using a powder that has been melt-atomised in an inert gas atmosphere from an aluminium or Al alloy with integrated hard materials, in particular from MMCs (metal matrix composites), reinforcing particles being added to the molten and atomised metal, in particular aluminium or an aluminium alloy, during or consecutive to the spraying process, and subsequently the powder particles being compressed by way of an SPS method in order to produce a component or a semi-finished product.

The invention relates to a method for producing components using a powder that has been melt-atomized in an inert gas atmosphere from an aluminum or Al alloy with integrated hard materials, in particular from MMCs (metal matrix composites) and to a component or semi-finished material in accordance with the method.

It is known to produce components from metals such as aluminum (Al) or Al alloys by spray compacting. In spray compacting, melts are atomized in an inert gas atmosphere (for example, nitrogen) and deposited on a target. Advantages of this method are the extremely high cooling rates and the potential for producing hypereutectic alloys. Such methods are described, for example, in EP 0198613, EP 0200349, EP 0574458, and EP 0517882.

It is also known in these methods to add ceramic particles such as SiC, B₄C or Al₂O₃ for reinforcement to create an MMC semi-finished material. The particles of the components (for example, SiC and Al) in the microstructure created in this way are present tightly connected.

In this method, in addition to the semi-finished material, so-called overspray, is also produced which can be supplied to the process again (re-injection) or can be treated further as a by-product. Alternatively, the MMC particles are introduced into the liquid Al melt during casting of the casting (Duralcan method).

In the similarly known SPS (spark plasma sintering) method, powders or powder mixtures are compressed, whereby an ideally optimal particle microstructure density for the application is created in the work piece or semi-finished material.

Disadvantages in the prior art (powder mixture) is, on the one hand, the incomplete bond between reinforcing particles and matrix, on the other hand the incomplete homogeneity of the mixture, which cannot be ensured. Both negatively affect the mechanical load capacity of the component produced using the mixture, a brake rotor for example. Subsequent consolidation (e.g. rolling, forging or extrusion) is additionally necessary to eliminate process-related residual porosity and to establish stable parameters and thus establish stable mechanical parameters.

The object of the invention is, therefore, to provide a method using which a component or semi-finished material is produced in which the reinforcing particles are bonded tightly and homogenously in the globular powder particles created by melt-atomizing, and no subsequent consolidation processes (e.g. rolling, forging or extrusion) are necessary.

This object is achieved by the invention by adding reinforcing particles, in particular aluminum or Al alloys, to the molten and atomized material during the spraying process or subsequent to said process.

Metal MMC powder particles (in particular Al), in which the reinforcing particles are imbedded tightly and homogenously, are generated during the atomization.

In the variation of the subsequent addition of MMC particles, MMC particles are added to the powder of aluminum or Al alloy previously created by melt-atomization after it is screened and mixed homogenously with said powder.

In all variations the powder particles are subsequently compressed using an SPS process to create a component or semi-finished material.

As a result, the MMC hard material distribution is extremely homogenous in the component created, which has a fundamentally positive effect on the microstructure and mechanical properties of this component or this semi-finished material.

In accordance with the invention, this is reinforced by the SPS process following atomization, which allows a high microstructure density (with a simultaneously very small grain size). Additional consolidation (e.g. rolling, forging or extrusion) of the component or semi-finished material created is no longer necessary.

If metal particles from overspray find a use, they are adjusted by screening to a grain spectrum <250 μm before being mixed with the reinforcing particles.

The previously listed metal alloy, or aluminum or Al alloy, to which the reinforcing particles are added consists, for example, of a hypereutectic aluminum alloy with a silicone content of 5 to 25 percent by weight, an iron content of 2 to 10 percent by weight, a nickel content of 2 to 5 percent by weight, a manganese content of 0 to 3 percent by weight, and a magnesium content of 0 to 1 percent by weight, the remainder is aluminum.

The MMC or hard material particles used advantageously have a size of 1 to 50 μm. For further treatment in the SPS process, the MMC powder particles created using the method described previously with a size smaller than or equal to 250 μm are used.

The invention also relates to the method, as described previously, as well as the method or semi-finished materials close to a final measurement, in particular those that have to withstand high mechanical and/or thermal stresses. Such components are, for example, brake rotors or friction rings for vehicles that can be produced advantageously using the method from the invention. In the case of a brake rotor or friction ring of this kind, it may be a mono-rotor, a ventilated rotor that was created by inserts or spacersby the SPS method or a multi-piece ventilated rotor.

Similarly, a brake rotor or friction ring of this type can be graded axially and/or radially in its microstructure according to load, i.e. its composition with respect to the MMC content can be distributed in accordance with the load across the component cross-section during production, as shown in FIG. 1.

Grading can also be achieved by additionally applying an MMC powder matched to the load to a homogenous base body as carrier as a functional layer using the SPS method, as shown in FIG. 2. 

What is claimed:
 1. Method for producing components using a powder melt-atomized in an inert gas atmosphere from aluminum or Al alloy with integrated hard materials, in particular from MMCs (metal matrix composites), characterized in that reinforcing particles are added to the molten and atomized metal, in particular aluminum or aluminum alloy, during the melting process or subsequently, and the powder particles are afterwards compressed to create a component or a semi-finished material using an SPS process.
 2. Method from claim 1, wherein the metal, or aluminum, content to which the MMC particles are added, consists of a hypereutectic aluminum alloy having a silicone content of 5 to 25 percent by weight, an iron content of 2 to 10 percent by weight, a nickel content of 2 to 5 percent by weight, a manganese content of 0 to 3 percent by weight, and a magnesium content of 0 to 1 percent by weight, the remainder is aluminum.
 3. Method from claim 1 or, wherein the globular MMC or hard material particles have a size of 1 to 30 μm.
 4. Method from claims 1 to 3, wherein the reinforcing particle content is 5 to 70 percent by weight.
 5. Method from claims 1 to 4, wherein further reinforcing particles, e.g. carbon short fibers are introduced into the metal during spraying or by mixing to improve further the mechanical properties of the material, or component or semi-finished material, produced in this way.
 6. Component, in particular brake rotor or friction ring, characterized in that it was produced using a method in accordance with one of the claims 1 to
 5. 